Arcuately shaped sanitary napkin and method of formation

ABSTRACT

A sanitary napkin having an absorbent core held in longitudinally arcuate configuration by a snug fitting substantially inelastic outer cover, the end extensions of which are fastened immediately adjacent each core end.

United States Patent Kokx July 18, 1972 ARCUATELY SHAPED SANITARY [56] References Cited NAPKIN AND METHOD OF UNITED STATES PATENTS FORMATION 3,284,856 11/1966 Hubin ..19/145 D H). K k G 2,964,04l 12/1960 Ashton et al. .....l28/290 [72] Inventor am Y o X men 5 3,106,207 10/1963 Dudley .128/290 N 1 Assisnw The Procter & Gamble Company, Cincm- 3,430,630 3/1969 Megison et a1... .....l28/290 nati, Ohio 3,445,897 5/1969 Franz "19/1445 [22] Filed: Sept 29, 1969 3,463,154 8/1969 Hendncks ..l28/287 {211 A No 861,772 Primary Examiner-Charles F1 Rosenbaum Attorney-John V. German 52 us. 01 ..12s/290,19/144.5 [57] ABSTRACT ..A6lt 13 16 Search ..128 284 287 290 2 96' A Sanitary napkin havmg absmbem We held In longitul4-OUTERWRAP WEB MATERIAL l2-ABSORBENT dinally arcuate configuration by a snug fitting substantially inelastic outer cover, the end extensions of which are fastened immediately adjacent each core end.

6 Claim, 4 Drawing Figures Patented July 18, 1972 l4-OUTERWRAP WEB MATERIAL IZ-ABSORBENT CORE 20'LINE OF SEWING INVENTOR.

Darrel D. Kokx TORNE Y ARCUATELY SHAPED SANITARY NAPKIN AND METHOD OF FORMATION FIELD OF THE INVENTION OF THE INVENTION Longitudinally arcuately configured sanitary napkins are well known in the prior art and shown, for example, in Luellen, U.S. Pat. No. 1,192,439, issued July 25, 1916; Johnson Jr., et al., U.S. Pat. No. 2,964,039, issued Dec. 13, 1960; Ashton et al., U.S. Pat. No. 2,964,041, issued Dec. 13, 1960; Bassett, U.S. Pat. No. 3,095,878, issued July 2, 1963; Morse, U.S. Pat. No. 3,236,238, issued Feb. 22, 1966; Megison et al., U.S. Pat. No. 3,430,630, issued Mar. 4, 1969; and Franz, U.S. Pat. No. 3,445,897, issued May 27, 1969. Such curved shape is desirable for a number of reasons well stated in such art; however, problems have been encountered in maintaining the curvature up to the point of application by the user since the devices are subject to package damage in shipment, high humidity conditions in storage, damage in handling prior to packaging and subsequent to opening, as for example, by the prospective user carrying the same in a purse, suitcase or the like. As a result, the napkins become flattened and this makes them more difficult to apply in curved form, develops the excessive transverse wrinkling sought to be avoided in the upper surface of the overwrap and makes the napkin less attractive in the eyes of the purchaser. These problems even adversely affect sanitary napkins employing preformed, unitary cores such as shown in some of the references listed above. Besides using the unitary core approach, other techniques for maintaining the arcuate shape of sanitary napkins have also been tried, including the use of rigid inserts or backing members and the shaped carton approach of Curran et al., U.S. Pat. No. 3,078,989, issued Feb. 26, 1963. To date, none of such measures have been successful in eliminating all of the problems mentioned.

OBJECTS OF THE INVENTION It is an object of the present invention to eliminate the above problems.

It is another object of the present invention to provide an overwrapped sanitary napkin of longitudinally arcuate configuration and in which the overwrap helps to maintain said arcuate configuration.

It is a further object of the present invention to provide an overwrapped sanitary napkin including a preformed unitary core of longitudinally arcuate configuration and in which the overwrap helps to maintain said arcuate configuration sub sequent to manufacture.

It is a still further object of the present invention to provide a method of forming an overwrapped longitudinally arcuately configured napkin in which such arcuate configuration is maintained by the overwrap web material.

SUMMARY OF THE INVENTION Briefly stated, in accordance with one aspect of the present invention there is provided a sanitary napkin comprising a longitudinally arcuately shaped core having a lower surface which in longitudinal dimension from end-to-end exceeds the corresponding dimension of the top surface thereof. The core is enclosed by an overwrap web material drawn snugly about the central transverse periphery of the core and longitudinally in each direction to the respective ends thereof. The overwrap is substantially inelastic in both longitudinal and transverse dimensions, preventing movement of the overwrapoutwardly of the central transverse periphery of the core in the absence of core compression. The overwrap extends outwardly beyond the ends of the core and is closed immediately adjacent the core ends by means which fasten the portion of the overwrap extending from the top surface of the core to the portion extending from the lower surface of the core, thereby retaining the snugness of longitudinal fit and maintain the curvature of the core.

In accordance with another aspect of the present invention there is provided a method of forming and securing a sanitary napkin in arcuate configuration. An absorbent core is trans- 0 versely snugly enclosed within an overwrap web material which extends longitudinally outwardly beyond the ends of the core. The enclosed core is bent into a longitudinally arcuate configuration about a support having a radius of curvature in the range of from about 2 to about 4 inches. Next, the concave surface of the overwrap is smoothed by tension applied in a longitudinal direction across the width of the end portions of the overwrap extending from the concave surface. The convex surface of the overwrap is then smoothed by tension applied across the width of the end portions of the overwrap extending from the convex surface without causing substantial deformation of the longitudinally central portion of the core. Finally, the juxtaposed end portions of the overwrap extending from the concave and convex surfaces at each end are fastened along lines immediately adjacent each end of the core.

BRIEF DESCRIPTION OF THE DRAWING While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the present invention, it is believed that the invention will be better understood from the following descrip tion taken in connection with the accompanying drawing in which:

FIG. 1 is a lengthwise extending vertical sectional view taken through a sanitary napkin of the present invention;

FIG. 2 is a plan view of the sanitary napkin of FIG. 1;

FIG. 3 is a fragmentary side view, partially in section and partially schematic of the napkin of FIG. 1 and apparatus with which the same can be formed; and

FIG. 4 is a fragmentary plan view similar to FIG. 2 but illustrating an alternative fastening means.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2, there is illustrated a longitudinally arcuately configured sanitary napkin 10 of the present invention which comprises an absorbent core 12 which is snugly enwrapped transversely and longitudinally with an onterwrap web material 14 having end sections 16 and 18 which can be inpleated at each side and thus flattened in a manner well known in the art. The end sections 16 and 18 extend outwardly from the ends of core 12 and serve as the means by which the napkin can be affixed to a sanitary belt. Because of its longitudinally arcuate shape, the top surface of sanitary napkin 10 is concave whereas the lower surface thereof is convex. The end-to-end longitudinal dimension of the lower surface is greater than the corresponding dimension of the top surface by at least about three percent but no more than about fifteen percent, since it is within this range that the present invention is operative to maintain the desired amount of longitudinally arcuate curvature without excessive transverse wrinkling of the overwrap web material in connection with sanitary napkins of conventional size. Preferably, the radius of curvature of the concave top surface of the sanitary napkin lies in the range of from about 3% to about 6 inches.

Portions 16a and 18a of end sections 16 and 18, respectively, extend from the concave top surface of the sanitary napkin l0 and oppositely disposed portions 16b and 18b extend from the convex lower surface thereof, constituting the broad faces of the flattened sections 16 and 18. Portions 16a and 16b are secured to one another by fastening means 20 extending along a line immediately adjacent the corresponding end of the core 12 and portions 18a and 18b are similarly secured by fastening means 20 immediately adjacent the other end of core 12.

The core 12 can be made of any suitably absorbent materials, but preferably is of a preformed, integral structure such as the unitary core structure of the aforesaid Megison et al. patent, the method and materials for core manufacture of said patent being hereby incorporated by reference. Although the drawings illustrate a core 12 structure which is generally rectangular in plan, it will be understood that the same can be of any desirable plan configuration such as, for example, one which is tapered at one or both ends for comfortable use or which has rounded edges.

In its final assembled condition, the compression strength of the core should be such that it does not compress to an extent greater than about 20 percent under a force of grams per square centimeter, in order for the napkin 10 to be held in longitudinally arcuate configuration. Although not critical, the absorbent core 12 can range in weight from about 6 to about 14 grams and can have a length of from about 7 to 9 inches and a width of from about 2 to about 3 inches. These size parameters can be altered as desired in accordance with the intended use or absorbent capacity required and play no part of the present invention.

The overwrap web material 14 can be any suitable fabric which is substantially inelastic (i.e., less than about 10 percent stretch) in both lengthwise and transverse dimensions under tensions up to the ultimate tensile strength in each direction. It should be smooth, soft, porous, liquid-permeable, non-pilling and sized as required by the size of the core 12. For example, the fabric can have a length of 19 inches and a width sufficient to encircle the transverse periphery of the core 12 with slight overlap. One very suitable such material is commercially available from Chicopee Mills, Inc., New York, N.Y. under the trademark VISKON and is assigned the code number A-230-552. This'is a rayon, nonwoven fabric which is line bonded by a resin along A; inch wide sinusoidal paths spaced at inch on centers. This fabric is white and has a caliper of about 4 to 5% mils, weighing approximately one-half ounce per square yard. The dry tensile strength in the machine direction (which would normally be placed lengthwise on the sanitary napkin) is about 2,000 grams per lineal inch and dry tensile strength-in the cross direction (placed transversely on the napkin) is about l00 grams per lineal inch.

The overwrap web material 14 is maintained in snug fitting circumferential contact with the core 12 by securement of the lengthwise extending edges thereof, not shown, preferably along the convex lower surface of the sanitary napkin 10. This can be accomplished by sewing or otherwise joining the overlapping lengthwise extending edges of the overwrap web material. One preferred method is the use of a hot melt adhesive bead along with the apparatus as described in Franz, US. Pat. No. 3,445,897, the disclosure of which is hereby incorporated by reference. As used herein snug fitting" requires that the overwrap web material 14 be subject to a finite amount of tension. This prevents the overwrap web material 14 from moving outwardly of the central transverse periphery of the core in the absence of core compression.

Although not shown, the sanitary napkin 10, can, if desired, also incorporate a moisture-impermeable film to prevent strikethrough of absorbed fluids and other special purpose enwrapments, inserts and the like, designed to improve the comfort and performance of the device.

The fastening means 20 can be any suitable device or material to effectuate the joinder of portions 160 and 16b, and 18a and 18b along lines immediately adjacent corresponding ends of the core 12. As shown in FIGS. 1 and 2, the fastening means 20 is a series of dots of conventional, commercially available hot melt adhesive. The dots are preferably small and spaced sufiiciently to retain the flexible and soft characteristics of the overwrap web material 14 throughout the line of securement. Dots comprising 56 inch diameter spots of hot melt adhesive, spaced one-quarter inch on center and using sufficient material to adhere the juxtaposed portions, are adequate for fastening the same while retaining softness. If a sufficiently soft and pliable adhesive is used, a continuous bead can be employed so that joinder is continuous throughout the line of securement. Other alternative fastening means can also be used, as exemplified in FIG. 4 wherein the fastening means 20' comprises a line of sewing.

Due to the snugness of fit of overwrap web material 14 in the longitudinal and transverse directions and to the compression characteristics of the core 12 and since the lines of securement by fastening means 20 prevent relative movement of the portions and 16b, and of portions 18a and 18b, the napkin is maintained in its desired longitudinally arcuate configurationunder normal conditions of handling and shipment. The core 12 resists flattening since such movement would require that the length of the portion of the substantially inelastic overwrap web material 14 which conforms to the concave top surface of the sanitary napkin be increased to the extent by which the concave surface is lengthened by such movement. Since such length of overwrap web material 14 is fixed by the means of securement 20, the flattening movement is prevented. In connection with the lengthening of the concave top surface of the core 12, it will be realized that if the core 12 is initially flat and then formed into the arcuate configuration, the top portion thereof is necessarily compressed and thereby shortened and flattening would reverse such conditions; on the other hand, if the core 12 is molded into the arcuate configuration, the top portion will be lengthened by tension as flattening occurs. This is, of course,,a simplistic explanation since oppositely directed forces will be found in the lower portion of the core and the ultimate result will necessarily involve an interaction of the two.

The sanitary napkin 10 of the present invention can be formed in the longitudinally arcuate shape and fastening means 20 applied in many different ways, however, the arrangement illustrated in FIG. 3 shows one preferred means and method. There is shown a cylindrical mandrel 22, the periphery of which is coated by a layer 22a of polytetrafluoroethylene. The thickness of the polytetrafluoroethylene layer 22a is not critical since the intended function thereof is to provide a surface with a low coefficient of friction and to prevent the adhesion of hot melt adhesives to the mandrel, as will be understood from the subsequent description. The outside diameter of the coated mandrel 22 is preferably in the range of from about 4 inches to about 8 inches, i.e., has a radius of curvature of from about 2 inches to about 4 inches, in order to result in a sanitary napkin 10 having a radius of curvature of from about 3% inches to about 6 inches following relaxation of the structure after manufacture.

At opposite sides of the mandrel 22 are hot melt applicator nozzles 26 through which melted hot melt adhesive can be controllably discharged. The nozzles 26 are circumferentially spaced around the mandrel 22 by an amount slightly greater than the length of the concave top surface of sanitary napkin 10 when it is formed about the mandrel 22, as shown. The nozzles 26 can be of any convenient structure, well within the design competence of those of ordinary skill in the art, and can, if desired, be mechanically actuated for radial and axial movement along the mandrel 22 to apply the above-described spaced dots or continuous bead of adhesive across the transverse dimension of the sanitary napkin 10. Alternatively, the nozzles 26 can comprise parts of hand-operated commercially available hot melt adhesive applicators.

As shown, the transversely enwrapped sanitary napkin such as that produced by the process and apparatus of Franz, US. Pat. No. 3,445,897, is formed about the periphery of mandrel 22 between the applicator nozzles 26 with the longitudinal dimension falling in a plane approximately perpendicular to the axis of the mandrel 22. Next, tension T is applied longitudinally across the width of portions 16a and 18a of overwrap web material 14, the tension being directed approximately tangentially of the mandrel 22 at points adjacent the ends of the core 12. The tension T is preferably in the range of from about 500 gm to about 2,000 gm, preferably from about 1,000 gm to about 1,500 gm per lineal inch. Such tension can be applied by any suitable means and can even be applied by hand. Those skilled in the art are readily able to devise mechanically operated tensioning devices if desired and for this reason, no disclosure is included herein.

Tension T is also applied in a longitudinal direction across the width of portions 16b and 18b of the overwrap web materiportions 16a and 16b are united along a line immediately adjacent the corresponding end of the absorbent core 12 and the portions 18a and 18b are similarly united along a line immediately adjacent the other end of the absorbent core 12. This can be done with the illustrated apparatus by pressing the portions to be united inwardly so that they contact and applying a continuous or discontinuous bead of hot melt adhesive thereto. The hot melt adhesive should be applied along lines substantially following the contour of the adjacent ends of the core and spaced outwardly therefrom by a small distance so that following removal of the sanitary napkin from the mandrel 22, subsequent relaxation of the structure results in the desired radius of curvature of the concave top surface.

If desired, following application of the tensions T and T in the core 12 and the overwrap surrounding it can be maintained in position and the end sections 16 and 18 twisted 180 adjacent the end of the core 12 and the fastening means applied across the twisted portions l6a-16b and 18a18b to retain the twist and provide the shape-retaining benefit previously described. Such twisting is especially beneficial in connection with the cores 12 of tapered shape since it helps the overwrap to conform to the shape of the core 12.

While particular embodiments of the invention have been illustrated and described, it will be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. For example, the end sections 16 and 18 can be of reduced length, terminating adjacent the fastening means 20 on the side removed from the core 12, and a different end tab material (for afiixment to a sanitary belt) attached to the sanitary napkin 10 by the fastening means 20. Thus, a stronger or special purpose end tab can be incorporated, if desired.

What is claimed is:

l. A longitudinally arcuately shaped sanitary napkin, comprising: a longitudinally arcuately shaped core and an overwrap web, said core having a lower surface which in longitudinal dimension from end-to-end exceeds the corresponding dimension of the top surface thereof, said core being completely enclosed by said overwrap web, said overwrap web being substantially inelastic in both longitudinal and transverse directions, said overwrap web drawn snugly about the central transverse periphery of said core, said overwrap web being also drawn snugly in both longitudinal directions from the central transverse periphery to the respective ends of said core, the transverse snugness preventing movement of said overwrap web outwardly of said central transverse periphery in the absence of compression of said core, said overwrap web extending outwardly beyond the ends of said core and having the poru'on thereof extending from the top surface of said core secured to the portion thereof extending from the lower surface of said core at each end thereof by fastening means along a transverse line of attachment, each said line of attachment being immediately adjacent its respective end of said core to retain the snugness of longitudinal fit thereon, thereby maintaining the arcuateness of said core.

2. The sanitary napkin of claim 1 in which the said core is a unitary, preformed structure having a compression strength sufficient to resist compression greater than about 20 percent under a force of 10 grams per square centimeter.

3. The sanitary napkin of claim 2 m which the said portions at each end are twisted said twist being maintained by said fastening means.

4. The sanitary napkin of claim 2 in which said fastening means closes said overwrap web material along lines substantially following the contour of the adjacent ends of said core and is selected from the group consisting of hot melt adhesive and lines of sewing.

5. The sanitary napkin of claim 1 in which said fastening means closes said overwrap material at each end along a line contacting substantially the entire periphery of the adjacent end of said core and in which said fastening means is selected from the group consisting of hot melt adhesive and lines of sewing.

6. The method of forming and securing a sanitary napkin in arcuate configuration which comprises:

A. transversely enclosing an absorbent core snugly within an overwrap web material which extends longitudinally outwardly beyond the ends of said core;

B. bending said enclosed core into a longitudinally arcuate configuration about a support having a radius of curvature in the range of from about 2 to about 4 inches;

C. smoothing the concave surface of the overwrap web material by longitudinally directed tension applied across the width of the end portions of the overwrap web material extending from said concave surface;

D. smoothing the convex surface of the overwrap web material by longitudinally directed tension applied across the width of the end portions of the overwrap web material extending from said convex surface,

said tension being insufficient to cause substantial deformation of the longitudinally central portion of said core; and

E. fastening the juxtaposed end portions of the overwrap web material extending from the concave and convex surfaces at each end along transverse lines immediately adjacent each end of said core.

i l l IF 

1. A longitudinally arcuately shaped sanitary napkin, comprising: a longitudinally arcuately shaped core and an overwrap web, said core having a lower surface which in longitudinal dimension from end-to-end exceeds the corresponding dimension of the top surface thereof, said core being completely enclosed by said overwrap web, said overwrap web being substantially inelastic in both longitudinal and transverse directions, said overwrap web drawn snugly about the central transverse periphery of said core, said overwrap web being also drawn snugly in both longitudinal directions from the central transverse periphery to the respective ends of said core, the transverse snugness preventing movement of said overwrap web outwardly of said central transverse periphery in the absence of compression of said core, said overwrap web extending outwardly beyond the ends of said core and having the portion thereof extending from the top surface of said core secured to the portion thereof extending from the lower surface of said core at each end thereof by fastening means along a transverse line of attachment, each said line of attachment being immediately adjacent its respective end of said core to retain the snugness of longitudinal fit thereon, thereby maintaining the arcuateness of said core.
 2. The sanitary napkin of claim 1 in which the said core is a unitary, preformed structure having a compression strength sufficient to resist compression greater than about 20 percent under a force of 10 grams per square centimeter.
 3. The sanitary napkin of claim 2 in which the said portions at each end are twisted 180*, said twist being maintained by said fastening means.
 4. The sanitary napkin of claim 2 in which said fastening means closes said overwrap web material along lines substantially following the contour of the adjacent ends of said core and is selected from the group consisting of hot melt adhesive and lines of sewing.
 5. The sanitary napkin of claim 1 in which said fastening means closes said overwrap material at each end along a line contacting substantially the entire periphery of the adjacent end of said core and in which said fastening means is selected from the group consisting of hot melt adhesive and lines of sewing.
 6. The method of forming and securing a sanitary napkin in arcuate configuration which comprises: A. transversely enclosing an absorbent core snugly within an overwrap web material which extends longitudinally outwardly beyond the ends of said core; B. bending said enclosed core into a longitudinally arcuate configuration about a support having a radius of curvature in the range of from about 2 to about 4 inches; C. smoothing the concave surface of the overwrap web material by longitudinally directed tension applied across the width of the end portions of the overwrap web material extending from said concave surface; D. smoothing the convex surface of the overwrap web material by longitudinally directed tension applied across the width of the end portions of the overwrap web material extending from said convex surface, said tension being insufficient to cause substantial deformation of the longitudinally central portion of said core; and E. fastening the juxtaposed end portions of the overwrap web material extending from the concave and convex surfaces at each end along transverse lines immediately adjacent each end of said core. 